The present invention relates to an N-substituted acrylamide copolymer, an intermediate product thereof, an aqueous composition of the N-substituted acrylamide copolymer, and an antistatic thermoplastic resin film, a thermoplastic resin film having a vapor deposition layer, a laminated thermoplastic resin film, a laminate comprising a foamed article and a resin layer, a support for recording sheets, an electroconductive paper, an electrostatic recording paper, a foamed article and a laminate of foamed articles.
Thermoplastic resins such as an olefinic resin, ABS resin and vinyl chloride resin hitherto have been formed into films or bags, which have been widely used as packaging materials or wrapping materials, parts of cars, and the like. Since the thermoplastic resins have high electric resistance, there is a serious defect in the thermoplastic resins that they are easily charged with electricity due to friction and dust is adhered to their surfaces thereby.
Recently, as the methods for imparting antistatic property to the thermoplastic resins, there have been proposed, for instance,
(A) a method comprising coating a solution of an antistatic agent on the surface of a resin and drying it. PA0 (B) a method comprising mixing an internal antistatic agent with a resin, PA0 (C) a method comprising coating a silicone compound on the surface of a resin, and PA0 (D) a method comprising modifying a resin itself, and the like. PA0 (A) In the process for preparing an electrostatic recording paper, substrate paper is coated with the electroconductive polymer followed by drying to form a low electric resistant layer, and it is once rolled up. Then, in the second step, it is rewound, and a solvent solution such as a toluene solution of vinyl chloride-vinyl acetate copolymer or styrene-acrylic acid copolymer is coated on the low resistant layer followed by drying to form a dielectric layer. Thus, an electrostatic recording paper is obtained. In the rewinding step, the low electric resistant layer becomes sticky or tacky due to blocking resulting from the properties of the electroconductive polymer. Therefore, the workability lowers and the quality of an obtained electrostatic recording paper is remarkably lowered. PA0 (B) In the process for preparing an electrostatic recording paper, there is a problem in solvent resistance, which is so-called "solvent holdout". After a low electric resistant layer is formed, a vinyl chloride-vinyl acetate copolymer, an acrylic acid-styrene copolymer or the like is coated thereon as a solution of a solvent such as toluene. At that time, the solvent is immersed into the inside of the low resistant layer to impair the formation of a dielectric layer and a low resistant layer, and as a result, recording property of an obtained electrostatic recording paper is lowered. PA0 (C) There is lowering of recording property depending upon humidity, which is a fatal defect of electrostatic recording paper. PA0 (A) it is necessitated to use an expensive silicone or fluorine-containing compounds, and that PA0 (B) all of the above-mentioned problems are not completely solved at the same time although tackiness, solvent resistance and moisture dependency of electric resistant are partially improved. PA0 (A) an abrasion resistance and washability resistance with water are excellent, that PA0 (B) transparency is excellent, that PA0 (C) there are no fine cracks on a resin surface, and that PA0 (D) heat resistance and chemical resistance are excellent. PA0 (A) a linear random N-substituted acrylamide copolymer comprising: PA0 (1) 65 to 99% by mole of ethylene units having the formula (I): EQU --(CH.sub.2 --CH.sub.2)-- (I) PA0 (2) 1 to 15% by mole of acrylate units having the formula (II): ##STR1## wherein R.sup.1 is an alkyl group having 1 to 4 carbon atoms, and (3) 1 to 35% by mole of acrylamide units having the formula (III): ##STR2## wherein R.sup.2 is an alkylene having 2 to 8 carbon atoms, R.sup.3 and R.sup.4 are the same or different and each is an alkyl group having 1 to 4 carbon atoms, R.sup.5 is an alkyl having 1 to 12 carbon atoms, an arylalkyl having 6 to 12 carbon atoms or an alicyclic alkyl having 6 to 12 carbon atoms, and X is a halogen atom, CH.sub.3 OSO.sub.3 -- or C.sub.2 H.sub.5 OSO.sub.3 --; and the copolymer has a weight average molecular weight of 1000 to 5000; PA0 (B) a linear random N-substituted acrylamide copolymer comprising: PA0 (1) 65 to 99% by mole of ethylene units having the above formula (I), PA0 (2) 1 to 15% by mole of acrylate units having the above formula (II) and PA0 (3) 1 to 35% by mole of acrylamide units having the formula (IV): ##STR3## wherein R.sup.2, R.sup.3 and R.sup.4 are the same as mentioned above, and the copolymer has a weight average molecular weight of 1000 to 50000; PA0 (C) an aqueous composition of the above N-substituted acrylamide copolymer; PA0 (D) an antistatic thermoplastic resin film comprising a thermoplastic resin containing 0.3 to 50% by weight of the above N-substituted acrylamide copolymer; PA0 (E) a thermoplastic resin film having a vapor deposition layer comprising an antistatic thermoplastic resin film containing 0.3 to 50% by weight of the above N-substituted acrylamide copolymer and a vapor deposition layer; PA0 (F) a laminated thermoplastic resin film having a thermoplastic resin layer containing the above N-substituted acrylamide copolymer; PA0 (G) a laminate comprising an olefinic resin foamed article and an olefinic resin layer containing the above N-substituted acrylamide copolymer; PA0 (H) a support for recording sheets comprising a substrate and an electroconductive layer containing the above N-substituted acrylamide copolymer; PA0 (I) an electroconductive paper comprising a paper having a layer of the above N-substituted acrylamide copolymer; PA0 (J) an electrostatic recording paper comprising a paper, a high resistant dielectric layer and an electroconductive layer comprising an olefinic resin containing the above N-substituted acrylamide copolymer; PA0 (K) a foamed article comprising an olefinic resin containing the above N-substituted acrylamide copolymer; and PA0 (L) a laminate of foamed articles having an olefinic resin foamed article layer containing the above N-substituted acrylamide copolymer.
According to the method (A), a solution of a surfactant is used as an antistatic agent. However, since the antistatic agent is easily removed from the surface of a resin by washing, permanent antistatic property cannot be given.
According to the method (B), as an internal antistatic agent, a glycerine fatty acid ester, a sorbitan fatty acid ester, an alkyldiethanolamide, a sodium alkylbenzenesulfonate, a quaternary salt of alkylimidazole, and the like have been used. When these internal antistatic agents are used, since antistatic property is maintained for a relatively long period of time since the antistatic agent is newly and successively bled out from the inside of the resin even when the antistatic agents are removed from the surface by washing. However, when these internal antistatic agents are used, it takes a long period of time for recovering the antistatic property after washing. Also, dust is rather easy to stick to the surface when the antistatic agent is bled out excessively. Further, there are disadvantages that it is necessary to add an excessive amount of the antistatic agent to the resin during processing and it is difficult to control the effective amount since the antistatic agent is volatilized due to, for instance, heat generated during molding at high temperatures because the agent has a low molecular weight.
In order to solve the defects of the above-mentioned internal antistatic agent, various high molecular weight compounds having an antistatic functional group have been proposed. For instance, Japanese Unexamined Patent Publication No. 170603/1989 proposes polymethyl methacrylate in which 20 to 80% by mole of methoxy groups are modified with diethanolamine. Japanese Examined Patent Publication No. 39860/1983 proposes a graft copolymer of an alkoxy polyethylene glycol methacrylate. Japanese Examined Patent Publication No. 29820/1989 discloses that a styrene-maleic anhydride copolymer modified with an imido group is cationized to form a quaternary one. Japanese Unexamined Patent Publication No. 121717/1987 proposes a comb-type copolymer of an aminoalkyl acrylate or acrylamide, and polymethyl methacrylate wherein the terminal carboxyl group is converted into methacryloyl group with glycidyl methacrylate and a cationic quaternary product thereof. However, all of the above-mentioned polymers cause the lowering of properties of the thermoplastic resin such as transparency and elongation, and their antistatic property and durability are insufficient.
The method (C) is disadvantageous in cost because the used silicone compounds are expensive and workability is low though the antistatic agent can be contained in a resin semipermanently.
According to the method (D) wherein a hydrophilic group is introduced into the thermoplastic resin, a large amount of hydrophilic groups should be introduced into the resin in order to give sufficient antistatic property to the resin. Such an introduction of a large amount of hydrophilic groups might result in lowering of moisture resistance and mechanical properties of the thermoplastic resin itself.
Generally, static electricity is remarkably generated on an olefinic resin film because of its large hydrophobic property. Accordingly, in case of using such a film as a packaging material, dust easily sticks, resulting in reducing of commercial values of contents, poor adhesion property, poor printing property and poor vapor deposition property, and also the end of the films is not turned up during rolling up. In addition, human body may be shocked by discharged static electricity and there is a fear of ignition in an atmosphere where a flammable organic solvent is used.
There is also a problem that vapor deposition of metal cannot be conducted to the olefinic resin film after a special surface treatment is conducted thereto since the film is poor in adhesion property due to its non-polarity.
In order to solve the above-mentioned problems, an olefinic resin film is prepared from a resin having a polar group such as a copolymer of ethylene and (meth)acrylic acid, a copolymer of ethylene and (meth)acrylic ester or a copolymer of ethylene and a vinyl compound having a glycidyl group, and the obtained film is subjected to corona discharge treatment in air or inert gas, or subjected to plasma treatment in inert gas, or the film is coated with an adhesive agent on which a metal is vapor deposited. However, when the polar group-containing resin is added thereto, a large amount of the resin should be added thereto in order to improve the adhesion property, so it becomes economically disadvantageous. When the copolymer having ethylene units is used, the film is shrunk or molten by the heat during vapor deposition since the more the ethylene content is, the lower the melting point becomes. As to various physical surface treatments, there are some problems as mentioned above.
Also, static electricity is remarkably generaged on a foamed article prepared from the olefinic resin, particularly an ethylene resin or a propyrene resin, because of their hydrophobic property. Therefore, dust sticks on the foamed article, or human body is shocked by discharged static electricity. Also, adhesive agents or printing inks cannot be coated uniformly on the surface of the foamed article, in other words, the adhesive agents or inks are repelled since the surface wettability with water is poor due to its high hydrophobic property, and adhesion property of the adhesive agent is wrong.
In order to improve the surface wettability of an olefinic resin foamed article, there is employed a method comprising conducting corona discharge treatment or a method comprising using a copolymer of ethylene and a vinyl monomer having a functional group or a graft copolymer.
However, when the method comprising conducting corona discharge treatment is employed, the surface wettability deteriorates with the passage of time, namely, permanent effect cannot be imparted. In case of using the above-mentioned copolymer, since a large amount of the copolymer should be added thereto to impart practical surface wettability of at least 37 dyne/cm to the foamed article, the cost increases and the thermal resistance lowers due to the low melting point of the copolymer.
A support for recording sheets is generally obtained in a manner wherein one side or both sides of a filmy substrate such as paper or a polyester film is coated with a macromolecule electrolyte such as polyvinylbenzyltrimethylammonium chloride or an electroconductive agent such as an ionic surfactant. However, since these electroconductive agents are hydrophilic and the electroconductivity depends upon humidity, when these electrolytes and electroconductive agents are used in the electrostatic recording paper, the electrostatic recording properties vary depending upon humidity.
In order to solve the above-mentioned problem, a metal is deposited by vapor deposition on a support, or a binder containing an electroconductive filler is coated on the support. However, according to these methods, a cost increases because of complicated processings. Also, when these methods are applied to a recording material for electrophotography, natural color of its material is lost since the material is colored.
Further, a conventional electroconductive agent has a hydrophilic group such as a cationic group or anionic group. To the contrary, since a lipophilic resin such as silicone, a vinyl chloride resin, a vinyl acetate copolymer, polyacrylate or polystyrene is used in a high resistant dielectric layer formed on an electroconductive layer, the affinity between the electroconductive layer and the high resistant dielectric layer is wrong. Therefore, the high resistant dielectric layer is not uniformly provided on the electroconductive layer, and images become unclear.
Also, as to an electroconductive agent having a relatively low molecular weight such as a weight average molecular weight up to 1000, since the electroconductive agent moves to a substrate or a high resistant dielectric article with the passage of time, recording properties are deteriorated.
According to a method comprising depositing a metal on a substrate by vapor deposition, the substrate is necessitated to be coated with an adhesive agent before the vapor deposition because there is no affinity between the metallic film and the high resistant dielectric layer. Also, according to a method comprising coating a binder containing an electroconductive filler, recorded images become unclear since the adhesion property varies depending upon the kind of the binders.
An electrostatic recording system has advantages that recording can be carried out at a high speed, and formed high quality images of high resolution can be semipermanently stored. Further, according to this system, since paper does not impair its natural feeling, it is used in a high speed facsimile apparatus, a monochroplotter or color for CAD and CAM, or the like.
The electrostatic recording paper used for the electrostatic recording system basically comprises paper as a substrate, a dielectric layer for maintaining an electrostatic charge and a low electric resistant layer which acts so that the dielectric layer is stably charged with an electric charge in various surroundings.
As the substrate paper of the electrostatic recording paper, high quality paper is mainly used, and an electroconductive layer is provided on one or both sides of the substrate paper to increase its electrostatic capacity, and a dielectric layer is formed on the electroconductive layer to have three or four layers. In order to form a low resistant layer, a method of coating an electroconductive polymer is usually employed. The electroconductive polymer takes an important role to give clear images, and influences electrostatic recording property.
As such an electroconductive polymer, there have been known, for instance, cationic polymers such as polyvinylbenzyltrimethylammonium chloride, polydimethyldiallylammonium chloride, polymethacryloyloxydiethyltrimethylammonium chloride and methacryloylamidopropyltrimethylammonium chloridediacetone acrylamide copolymer, anionic polymers such as sodium polystyrene sulfonate and polystyrene sulfonate ammonium, and the like. However, in case of using the electroconductive polymer, the following problems have been pointed out.
The electric resistance of the conventional electroconductive agent greatly varies depending upon humidity of surroundings. The electric resistance is relatively low in high humidity and it is relatively high in low humidity. Consequently, recording density is greatly influenced by the humidity of surroundings.
Accordingly, as the electroconductive agent used in the electrostatic recording paper, a material having no stickiness (tackiness), excellent solvent resistance, and small moisture dependency is desired.
In the above-mentioned circumstances, there have been proposed a method comprising using a composition containing 0.1 to 10% by weight of organic silicone as an electroconductive agent from the viewpoint of the improvement of tackiness (Japanese Unexamined Patent Publication No. 2362/1982), a method comprising using a copolymer of quaternary diallyldimethylammonium chloride and a fluorine-containing monomer such as octafluoropentyl methacrylate (Japanese Unexamined Patent Publication No. 60510/1980) or a method comprising using a copolymer of a water-soluble quaternary ammonium monomer such as vinylbenzyltrimethylammonium chloride or dimethyldiallylammonium chloride and acrylamide (Japanese Unexamined Patent Publication No. 86842/1980) from the viewpoint of the improvement of solvent resistance, and the like.
In order to improve both of tackiness and solvent resistance, there have been proposed a method comprising using a fluoro-surface active agent and a stabilizer together with the above-mentioned electroconductive agent (Japanese Unexamined Patent Publication No. 66944/1980), a method comprising providing a barrier layer made of fluorocarbon on a low resistant layer (Japanese Unexamined Patent Publication No. 112398/1980), and the like. As a method for satisfying tackiness and humidity dependency of electric resistance, there have been proposed a method comprising using a cellulose derivative substituted by 2,3-epoxytrialkylammonium chloride (Japanese Unexamined Patent Publication No. 73773/1980), a method comprising using a copolymer of an epihalohydrine and a monoamine or polyamine (Japanese Unexamined Patent Publication No. 63799/1986), a method comprising using a copolymer of a diallyldialkylammonium chloride and a vinyl acetamide monomer (Japanese Unexamined Patent Publication No. 267385/1987), and the like.
However, the above methods still have the problems that
An object of the present invention is to provide a copolymer which semipermanently possesses excellent antistatic property, which does not impair physical properties of resins by the addition of the copolymer or does not cause blocking in a final product, which is excellent in all of properties required for coating of an antistatic agent as mentioned below, and which is suitable for the uses such as an antistatic agent and an aqueous composition.
The properties required for the antistatic agent are described in a column of performances required for an antistatic agent for coating in "Practical Handbook for Plastics and Rubbers" (1987) Kabushiki Kaisha Kagaku Kogyosha p. 395, that is, there are required that
A further object of the present invention is to provide an antistatic thermoplastic resin film and an olefinic resin foamed article laminate which is excellent in antistatic property, which has no bleeding or blocking, and which has a metal vapor deposition layer with excellent adhesion.
A still further object of the present invention is to provide a support for recording sheets, an electrostatic recording paper and an electroconductive substrate, which are excellent in electroconductivity and affinity between the electroconductive layer and the high resistant dielectric layer.
A still further object of the present invention is to provide an olefinic resin foam, which is excellent in antistatic property and surface wettability, which has no bleeding or blocking, and which is excellent in printability.
These and other objects of the present invention will become apparent from the description hereinafter.